My God. It's Full of Black Holes.

The image above doesn't look like much at a glance, does it? Look again. What you're seeing are thousands of black holes. Thousands. That image is a part of the Chandra Deep Field South, the result of a series of very long exposures of one small section of the sky using the space-based Chandra X-Ray Observatory. Astronomers combined images taken over the 18-year period from 1999 to 2016, creating a stacked image that's the equivalent of a single 7,016,500 second exposure. That's over 81 days. So...